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This study presents 53-year climatology of Southern Hemisphere (SH) blockings in the winter using daily 500-hPa geopotential height data from NCEP-NCAR reanalysis. The variability of SH blocking events and their relationships with combined phases of El Niño/southern oscillation (ENSO) and the southern annular mode (SAM) are examined. Conventional indices were revised and a slightly modified index is proposed to detect latitudinal variations of SH blockings. The South Pacific region is examined in detail. There is no statistically significant long-term trend in the SH blockings. During moderate El Niño, the preferred location SH blocking is observed over East Pacific, and we show that the blocking frequency increases during negative SAM phases. During moderate La Niña the SH blockings are significantly suppressed over Central Pacific, with lower blocking frequency during positive SAM phases. These results indicate that the daily variability of SH blocking is strongly modulated by both ENSO and SAM phases. © 2013 Royal Meteorological Society.

The number of paleoprecipitation records from the South American Monsoon domain that cover the last millennium has increased substantially in past years. However, hitherto most studies focused only on regional aspects, thereby neglecting the role of large‐scale monsoon variability and the mechanisms that link proxy locations in space and time. Here we decompose the South American Monsoon into its main modes of variability by applying a Monte Carlo principal component analysis to a compilation of 11 well‐dated summer paleoprecipitation records from tropical South America. The first mode represents changes in precipitation over the core monsoon domain, while the second mode is characterized by high loadings along the fringes of the South American Monsoon over Southeastern South America and the northern monsoon limit. Composite analysis reveals an enhanced monsoon with a wider, rather than a southward displaced, South Atlantic Convergence Zone during the early Little Ice Age, in contrast to previous interpretations. Plain Language Summary: The South American Monsoon is responsible for more than 70% of the annual precipitation falling over tropical South America. Due to the lack of data prior to the middle of the twentieth century, the long‐term variability of the monsoon is poorly understood. Yet there are concerns that increasing greenhouse gas concentrations may significantly modify monsoon behavior in the 21st century. To better understand how the monsoon responds to such perturbations, detailed knowledge of how it varied in the past is crucial. This will facilitate improvements to Earth System Models that are used to project future rainfall changes in the region. Here 11 paleoprecipitation records that span the last millennium are analyzed using statistical techniques that allow extracting the shared variability from all records. Our result highlight how the monsoon responded in space and time to large‐scale perturbations of the climate system, associated with the Little Ice Age and the Medieval Climate Anomaly. Key Points: We use high‐resolution δ18O records to decompose the South American Monsoon into its main modes of variability during the last millenniumThe first mode shows an enhanced monsoon during the Little Ice Age and a weakening during the Medieval Climate AnomalyThe second mode represents monsoon variability along the fringes of the monsoon area and indicates periods of widening/contractions of the monsoon axis [ABSTRACT FROM AUTHOR]

This paper reviews recent progress made in our understanding of the functioning and variability of the South American Monsoon System (SAMS) on time scales varying from synoptic to long-term variability and climate change. The SAMS contains one of the most prominent summertime climate patterns in South America, featuring a strong seasonal variability in a region lying between the Amazon and the La Plata Basin. Much of the recent progress is derived from complementary international programs, such as the Monsoon Experiment South America (MESA), as well as from ongoing international programs such as the Large Scale Biosphere Atmosphere Experiment in the Amazon Basin (LBA) and the La Plata Basin (LPB) Regional Hydroclimate Project, which includes the CLARIS LPB Europe-South America Network for Climate Change Assessment and Impact Studies in La Plata Basin Project. The latter assesses atmosphere-land surface interactions, the role of land use changes and aerosols from biomass burning considered as sources of variability and change in the SAMS functioning, characteristics and behaviour. The SAMS region is particularly susceptible to variations of climate due to the importance of hydroelectricity generation and the agricultural base of local economies. Also addressed in this report are projections of climate change and extremes, which are important for impact and vulnerability assessments. This discussion includes the need to identify and understand important processes that control the monsoonal climate, how these processes may vary and change, and how they may interact with key societal sectors, including water resource management, hydroelectric generation, agriculture, and agribusiness. This paper reports on the major contributions of MESA to the knowledge of characteristics, functioning and variability of the SAMS, and is based on recent studies and publications, and can be considered as an update of a previous review by C. S. Vera et al. (2006a). Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The impact of the inter-El Niño (EN) variability on the moisture availability over Southeastern South America (SESA) is investigated. Also, an automatic tracking scheme was used to analyze the extratropical cyclones properties (system density - SD and central pressure - CP) in this region. During the austral summer period from 1977–2000, the differences for the upper-level wave train anomaly composites seem to determine the rainfall composite differences. In fact, the positive rainfall anomalies over most of the SESA domain during the strong EN events are explained by an upper-level cyclonic center over the tropics and an anticyclonic center over the eastern subtropical area. This pattern seems to contribute to upward vertical motion at 500 hPa and reinforcement of the meridional moisture transport from the equatorial Atlantic Ocean and western Amazon basin to the SESA region. These features may contribute to the positive SD and negative CP anomalies explaining part of the positive rainfall anomalies found there. On the other hand, negative rainfall anomalies are located in the northern part of SESA for the weak EN years when compared to those for the strong events. Also, positive anomalies are found in the southern part, albeit less intense. It was associated with the weakening of the meridional moisture transport from the tropics to the SESA that seems have to contributed with smaller SD and CP anomalies over the most part of subtropics, when compared to the strong EN years. [ABSTRACT FROM AUTHOR]

The impact of the maximum convection location over eastern and central Equatorial Pacific over the intensity and positioning of the South American Low-Level Jet east of the Andes (SALLJ) during the austral summer was investigated. The Bonner criteria 1 was applied to the NCEP-NCAR circulation fields during the El Niño of 1997/1998 and 2002/2003 to identify the SALLJ episodes. The composites of the atmospheric circulation over the South America during El Niño events showed that the SALLJ can be influenced by small displacements of the quasi-stationary Rossby waves position. During the strong El Niño event of 1997/1998 the SALLJ is maintained by the eastern trade winds. A low-level anomalous anticyclonic circulation over the central part of Brazil enhanced the wind in the nucleus of the jet and displaced its axis to the Northern Argentina and South of Brazil. However, the northern trade winds seem to maintain the SALLJ during the weak El Niño of 2002/2003. The jet was weaker and displaced more southeastward of Brazil than during the strong event. [ABSTRACT FROM AUTHOR]

Previous studies have discussed the interannual variability of a meridional seesaw of dry and wet conditions over South America (SA) associated to the modulation of the South Atlantic Convergence Zone (SACZ). However, they did not explore if the variability inter ENSO (El Niño Southern Oscillation) can be related to the phase changes of this dipole. To answer this question, an observational work was carried out to explore the atmospheric and Sea Surface Temperature (SST) conditions related to the same ENSO signal and to opposite dipole phases. Rotated Empirical Orthogonal Function (REOF) analysis was applied over normalized Chen precipitation seasonal anomalies in order to find the dipole mode in the Austral Summer (December to February). The fourth rotated mode, explaining 6.6% of the total variance, consists of positive loading over the SACZ region and negative loading over northern Argentina. Extreme events were selected and enhanced activity of SACZ during the Summer season (SACZ+) was identified in nine years: five during La Niña events (LN) and two in El Niño episodes (EN). On the other hand, inhibited manifestations of this system (SACZ-) were identified in seven years: four in EN and two during LN. Power spectrum analysis indicated that the interannual variability of the precipitation dipole seems to be related to the low frequency and to the quasi-biennial part of ENSO variability. The ENSO events with the same signal can present opposite phases for the dipole. The results suggest that the displacement of the convection over Indonesia and western Pacific can play an important role to modulate the seesaw pattern. [ABSTRACT FROM AUTHOR]

Abstract: The impact of Indian Ocean Dipole (IOD) mode events on austral surface air temperature (SAT) variability was studied both by statistical analysis of observed/assimilated data and experiments with a mechanistic baroclinic atmospheric model. During the period of analysis (January 1958–December 1999), IOD events had the strongest impact on SAT anomalies during austral spring and hence, the analysis was focussed on this season. IOD events induced large scale, intercontinental correlations of SAT anomalies amongst Australia, Africa and South America. Surface temperature consistently rose (fell) abnormally and coherently in the subtropical regions of these continents during positive (negative) IOD events. Variability during non-IOD years was considerably weaker than during IOD years over these regions. Analysis of stream function anomalies at the 200 hPa level (source: NCEP/NCAR reanalysis) revealed a Rossby-wave train extending from the eastern Indian Ocean into the subtropical regions of the Pacific and Atlantic oceans. Further, the diagnosed Rossby-wave activity flux emanated from the eastern Indian Ocean and propagated along the subtropical and subpolar jet streams qualitatively in agreement with linear wave dynamics. Experiments with idealized forcing in a primitive equation mechanistic atmospheric model suggested that tropical convective anomalies in the Indian Ocean during IOD events likely affects the austral subtropics through stationary Rossby-wave propagation. [Copyright &y& Elsevier]

Large-scale epidemics of arboviruses, such as dengue, have heightened societal awareness regarding the necessity of combating the primary transmission vectors. Equally critical is the identification of environmental conditions and variables that influence vector population dynamics. Aedes aegypti , the primary vector of arboviruses such as dengue and Zika in Brazil, is closely associated with the climatic and geographical conditions of urban environments. This study examines the relationship between precipitation and confirmed dengue cases in Recife (Brazil), employing regression and quantile analyses to evaluate the influence of meteorological conditions on the disease's spread. The findings reveal a direct correlation between monthly averages of precipitation and confirmed cases, although this is apparent only when excluding years of epidemic peaks. The highest number of cases generally aligns with the rainy season, and the lowest with the dry season, with weak, moderate and strong precipitation events being closely linked to increased dengue incidence. However, notable discrepancies were identified: four out of six major outbreaks occurred in drier months, challenging the assumption of a straightforward relationship between rainfall and dengue incidence. These findings underscore the multifaceted nature of dengue dynamics, suggesting that while precipitation plays a significant role, other factors, including serotype circulation and broader climatic phenomena, are equally critical in driving outbreaks. This complexity highlights the need for a more comprehensive understanding of the mechanisms influencing dengue epidemics., Competing Interests: The authors have no relevant financial conflicts of interest. However, it should be noted that Tiago Massoni, Patty Kostkova, Tercio Ambrizzi, and Anwar Musah are members of the Editorial Board of Vector-Borne Diseases -- The Digital One Health Approach. Due to this affiliation, the manuscript has been managed by other editorial members. These author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Borges, Musah, Dutra, Tunali, Lima, Tunali, da Silva, Aldosery, Moreno, dos Santos, Massoni, Yenigün, Kostkova, da Rocha, Campos and Ambrizzi.)

This study aims to evaluate the position and intensity of the South Atlantic Subtropical High (SASH), related to sea ice extent (SIE) retraction and expansion in the Weddell Sea, assessing precipitation in South America. We assess the difference between atmospheric fields related to SIE (four most intense retraction events minus four most intense expansion events) in February. To this end, we used NSIDC SIE, ERA-5 reanalysis, CHIRPS precipitation, ICOADS SST, ONI/SAM indexes (CPC/NOAA). In the following month, under neutral ENSO and SAM, we observed tropospheric warming in the Weddell Sea and cooling in the mid-latitudes South Atlantic. There is a weakening of both the Weddell Sea circumpolar low and the high pressures between tropical and subtropical latitudes, in addition to the equatorward shift of the Ferrel cell. Therefore, SASH weakens and contracts, resulting in a reduction of the tropical Atlantic moisture supply to South America and negative precipitation anomalies in the tropical region - similar to the suppression pattern of the South Atlantic Convergence Zone. Our results suggest that SIE retraction (expansion) in the Weddell Sea may contribute to the weakening (strengthening) of the SASH and an early-ending (longer-ending) or drier-ending (wetter-ending) rainy season in tropical South America.

This study investigated whether there are differences in the frequency and position of Southern Hemisphere atmospheric blockings between Coupled Model Intercomparison Project Phase 5 models with different representations of Antarctic sea ice extent in historical experiments. In the model with the greatest sea ice underestimation (Model for Interdisciplinary Research on Climate version 5) there is a weakening of the polar jet and an increase in 500-hPa height. These atmospheric conditions favor the predomination of simulated blocking frequency overestimations (autumn-winter), in relation to the observed (ERA-Interim). On the other hand, in the models with the greatest sea ice overestimations (Community Climate System Model version 4) and the better sea ice representation (Norwegian Earth System Model version 1) there is a strengthening of the polar jet and weaker positive differences in 500-hPa height in the Antarctic region. These atmospheric conditions favor a predominance of simulated blocking frequency underestimations (all seasons). All models present a good representation of the preferred blocking regions (South Pacific), although they do not represent the longitudinal location of the maximum frequency. In years of sea ice retraction (expansion), there is a predominance of a higher (lower) blocking frequency in the 60°S for all models and observed data.

Oceanic heat sources disturb the atmosphere, which, to come back to its initial state, disperses waves. These waves affect the climate in remote regions, characterizing the teleconnection patterns. In this study, we describe eight teleconnection patterns that affect South America climate: the El Niño-Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), the Atlantic Multidecadal Oscillation (AMO), the Tropical Atlantic Dipole (TAD), the South Atlantic Dipole (SAD), the Southern Annular Mode (SAM), the Madden-Julian Oscillation (MJO), and the Indian Ocean Dipole (IOD). Precipitation and winds at 850-hPa anomalies, considering these teleconnection patterns in ENSO neutral periods, are also presented. Overall, southeastern South America and the north sector of the North and Northeast regions of Brazil are the most affected areas by the teleconnection patterns. In general, there is a precipitation dipole pattern between these regions during each teleconnection pattern., (© 2021 New York Academy of Sciences.)

Mosquito surveillance is a crucial process for understanding the population dynamics of mosquitoes, as well as implementing interventional programs for controlling and preventing the spread of mosquito-borne diseases. Environmental surveillance agents who performing routine entomological surveys at properties in areas where mosquito-borne diseases are endemic play a critical role in vector surveillance by searching and destroying mosquito hotspots as well as collate information on locations with increased infestation. Currently, the process of recording information on paper-based forms is time-consuming and painstaking due to manual effort. The introduction of mobile surveillance applications will therefore improve the process of data collection, timely reporting, and field worker performance. Digital-based surveillance is critical in reporting real-time data; indeed, the real-time capture of data with phones could be used for predictive analytical models to predict mosquito population dynamics, enabling early warning detection of hotspots and thus alerting fieldworker agents into immediate action. This paper describes the development of a cross-platform digital system for improving mosquito surveillance in Brazil. It comprises of two components: a dashboard for managers and a mobile application for health agents. The former enables managers to assign properties to health workers who then survey them for mosquitoes and to monitor the progress of inspection visits in real-time. The latter, which is primarily designed as a data collection tool, enables the environmental surveillance agents to act on their assigned tasks of recording the details of the properties at inspections by filling out digital forms built into the mobile application, as well as details relating to mosquito infestation. The system presented in this paper was co-developed with significant input with environmental agents in two Brazilian cities where it is currently being piloted., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Aldosery, Musah, Birjovanu, Moreno, Boscor, Dutra, Santos, Nunes, Oliveira, Ambrizzi, Massoni, dos Santos and Kostkova.)

This paper explores the main factors for mosquito-borne transmission of the Zika virus by focusing on environmental, anthropogenic, and social risks. A literature review was conducted bringing together related information from this genre of research from peer-reviewed publications. It was observed that environmental conditions, especially precipitation, humidity, and temperature, played a role in the transmission. Furthermore, anthropogenic factors including sanitation, urbanization, and environmental pollution promote the transmission by affecting the mosquito density. In addition, socioeconomic factors such as poverty as well as social inequality and low-quality housing have also an impact since these are social factors that limit access to certain facilities or infrastructure which, in turn, promote transmission when absent (e.g., piped water and screened windows). Finally, the paper presents short-, mid-, and long-term preventative solutions together with future perspectives. This is the first review exploring the effects of anthropogenic aspects on Zika transmission with a special emphasis in Brazil., (© 2021. The Author(s).)

Our paper reviews recent progress in the study and understanding of observed trends in extreme rainfall events in the Metropolitan Area of São Paulo (MASP). These are discussed in relation to hydrometeorological hazards that trigger natural disasters, such as flash floods, landslides, and droughts, that affect the population and local economies. A review of the most updated literature on rainfall and extremes in the MASP shows a significant increase in the total volume of rainy-season rainfall during the last seven decades. While there were practically no days with heavy rain (more than 50 mm) in the 1950s, these days have been occurring two to five times a year in the last 10 years. This, together with the inappropriate occupation of risky areas, such as slopes and banks of watercourses, leads to inundation, flooding, and landslides. Changes in extremes can be partly due to natural climate variability but can also be related to global warming and/or urbanization. There is ample evidence of an increasing risk of rainfall-related hazards in the MASP. This is particularly so for landslides in vulnerable areas. Exposure will continue to lead to risk increases. This calls for significant improvement in climate and disaster risk reduction and management efforts in the MASP region., (© 2020 New York Academy of Sciences.)

Regional climate models have been used since 1989 in order to improve climate simulation in regions where mesoscale forcings modulate the regional climate. These models are driven by time-dependent lateral boundary conditions from global climate models or reanalysis, and this process is called dynamical downscaling. Here, we review the evolution of regional climate modeling, as well as present the studies developed for South America., (© 2018 New York Academy of Sciences.)

The aim of this paper is to analyze the relationship between North Atlantic Oscillation (NAO), meteorological variables, air pollutants, and hospital admissions due to diseases of circulatory systems in Lisbon (Portugal) during winter months (2003-2012). This paper is one of the few studies analyzing the impact of NAO on health through its influence on thermal stress and air pollution and is the first to be conducted in Lisbon. This study uses meteorological data (synthetized into a thermal comfort index), air pollutant metrics, and the NAO index (all clustered in 10-day cycles to overcome daily variability of the NAO index). The relationship between morbidity, thermal comfort index, NAO index, and air pollutants was explored through several linear models adjusted to seasonality through a periodic function. The possible indirect effect between the NAO index and hospital admissions was tested, assuming that NAO (independent variable) is affecting hospital admissions (outcome variable) through thermal discomfort and/or pollution levels (tested as individual mediators). This test was conducted through causal mediation analysis and adjusted for seasonal variation. The results from this study suggest a possible indirect relationship between NAO index and hospital admissions. Although NAO is not significantly associated with hospital admissions, it is significantly associated with CO, PM 2.5 , NO, and SO 2 levels, which in turn increase the probability of hospitalization. The discomfort index (built with temperature and relative humidity) is significantly associated with hospital admissions, but its variability is not explained by the NAO index. This study highlights the impacts of the atmospheric circulation patterns on health. Furthermore, understanding the influence of the atmospheric circulation patterns can support the improvement of the existing contingency plans.

Our objective was to assess extrinsic influences upon childbirth. In a cohort of 1,826 days containing 17,417 childbirths among them 13,252 spontaneous labor admissions, we studied the influence of environment upon the high incidence of labor (defined by 75th percentile or higher), analyzed by logistic regression. The predictors of high labor admission included increases in outdoor temperature (odds ratio: 1.742, P = 0.045, 95%CI: 1.011 to 3.001), and decreases in atmospheric pressure (odds ratio: 1.269, P = 0.029, 95%CI: 1.055 to 1.483). In contrast, increases in tidal range were associated with a lower probability of high admission (odds ratio: 0.762, P = 0.030, 95%CI: 0.515 to 0.999). Lunar phase was not a predictor of high labor admission (P = 0.339). Using multivariate analysis, increases in temperature and decreases in atmospheric pressure predicted high labor admission, and increases of tidal range, as a measurement of the lunar gravitational force, predicted a lower probability of high admission.

This work examines the sources of moisture affecting the semi-arid Brazilian Northeast (NEB) during its pre-rainy and rainy season (JFMAM) through a Lagrangian diagnosis method. The FLEXPART model identifies the humidity contributions to the moisture budget over a region through the continuous computation of changes in the specific humidity along back or forward trajectories up to 10 days period. The numerical experiments were done for the period that spans between 2000 and 2004 and results were aggregated on a monthly basis. Results show that besides a minor local recycling component, the vast majority of moisture reaching NEB area is originated in the south Atlantic basin and that the nearby wet Amazon basin bears almost no impact. Moreover, although the maximum precipitation in the "Poligono das Secas" region (PS) occurs in March and the maximum precipitation associated with air parcels emanating from the South Atlantic towards PS is observed along January to March, the highest moisture contribution from this oceanic region occurs slightly later (April). A dynamical analysis suggests that the maximum precipitation observed in the PS sector does not coincide with the maximum moisture supply probably due to the combined effect of the Walker and Hadley cells in inhibiting the rising motions over the region in the months following April.

Precipitation and temperature climate indices are calculated using the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis and validated against observational data from some stations over Brazil and other data sources. The spatial patterns of the climate indices trends are analyzed for the period 1961-1990 over South America. In addition, the correlation and linear regression coefficients for some specific stations were also obtained in order to compare with the reanalysis data. In general, the results suggest that NCEP/NCAR reanalysis can provide useful information about minimum temperature and consecutive dry days indices at individual grid cells in Brazil. However, some regional differences in the climate indices trends are observed when different data sets are compared. For instance, the NCEP/NCAR reanalysis shows a reversal signal for all rainfall annual indices and the cold night index over Argentina. Despite these differences, maps of the trends for most of the annual climate indices obtained from the NCEP/NCAR reanalysis and BRANT analysis are generally in good agreement with other available data sources and previous findings in the literature for large areas of southern South America. The pattern of trends for the precipitation annual indices over the 30 years analyzed indicates a change to wetter conditions over southern and southeastern parts of Brazil, Paraguay, Uruguay, central and northern Argentina, and parts of Chile and a decrease over southwestern South America. All over South America, the climate indices related to the minimum temperature (warm or cold nights) have clearly shown a warming tendency; however, no consistent changes in maximum temperature extremes (warm and cold days) have been observed. Therefore, one must be careful before suggesting any trends for warm or cold days.